Plain bearing and wind energy unit with said bearing

ABSTRACT

In a plain bearing for the transmission of high axial forces and great flexural moments with slight relative movements the one co-operating bearing component has an annular rib which engages into an annular groove provided on the other co-operating bearing component. The annular rib which can be of an outwardly convergent trapezoidal cross-section is provided with anti-friction linings on its free side faces and possibly peripheral faces. The anti-friction linings, like the co-operating bearing component in question, in particular an outer ring carrying the annular rib, can be subdivided segment-like. The segments can then be released individually from their composite assembly and maintained, in particular provided with new anti-friction linings. A preferred use of this plain bearing is the arrangement thereof between a pylon-supported machine head and the pylon head of a wind power installation.

The invention concerns a plain bearing for the transmission of highaxial forces and large flexural moments with small relative movementsbetween the co-operating bearing components and a wind powerinstallation with such a plain bearing between its pylon-supportedmachine head and the pylon head.

Plain bearings involving the demand profile as specified above can beused for example as pivot bearings in cranes, certain leisure andpleasure installations and indeed wind power installations (as so-calledazimuth bearings). In that respect, a structural problem arises out ofthe fact that, even in the case of a vertical rotary axis, the forces,both in the direction of an applied load and also in the lifting-offdirection, have to be carried by the bearing.

To attain the object which derives therefrom, in its general aspect theinvention provides that an annular rib arranged on one co-operatingbearing component engages into an annular groove provided on the otherco-operating bearing component. In this case the annular rib may be ofboth a rectangular cross-section and also an outwardly convergingtrapezoidal cross-section; it is advantageously provided withanti-friction linings on its free side faces and on its peripheralfaces. The anti-friction linings can be omitted in the case of atrapezoidal rib cross-section.

In order to be able to more easily replace the anti-friction liningswhich are inevitably subjected to wear, a development of the inventionprovides that the anti-friction linings are subdivided segment-like andare fixedly but releasably connected to the rib.

In particular in such a case it can further be provided that one of theco-operating bearing components is subdivided segment-like and thesegments are releasable individually from their composite assembly. Inparticular the annular rib which is fitted with the anti-frictionlinings can be subdivided into segments and can be of such aconfiguration/arrangement that it engages radially from the outside intothe inwardly disposed annular groove. Then the annular rib segments withthe anti-friction lining segments secured thereto can be graduallyreleased (in the peripheral direction) from their composite assembly andtheir fixing to the load-bearing or supported component, and pulledradially outwardly, and inserted again after having been fitted with newanti-friction lining segments. It will be appreciated that replacementby a substitute rib member provided with new anti-friction liningsegments is also possible.

It will be appreciated that all arrangements can also be respectivelyreversed. Thus, the anti-friction linings can also be arranged at theinside surfaces of the annular groove which is subdivided segment-likeand which engages from the outside over the inwardly disposed annularrib. In addition the respective inwardly disposed component (annular ribor annular groove) can be subdivided into segments. Then however theoutwardly diverging wedge shape of the segments is a hindrance in regardto their being pulled out inwardly. In that case therefore the segmentsare to be edged in parallel relationship and compensating elements arepossibly to be provided between the segments carrying the anti-frictionlinings.

In order to make it easier to replace the segments, it is possible toprovide power-operated means such as for example pneumatically orhydraulically piston-cylinder units between the co-operating bearingcomponents, which simultaneously engage them only in the stationarycondition and which are capable of lifting the co-operating bearingcomponent which is bearing downwardly, with respect to the bearingcomponent supporting same, so that the fixing of the segments can bereleased and they can be withdrawn. After they have been refitted, thefixing of the load-relief means, at least to one of the co-operatingbearing components, is released again.

In its specific aspect the invention further concerns a wind powerinstallation having a plain bearing of the above-described kind betweena pylon-supported machine head and the pylon head, wherein providedbetween the pylon head and the machine head is a tracking drive forrotation of the machine head about the vertical axis of the pylon, independence on wind direction, wherein the plain bearing is adapted toguide the machine head in the radial and in the axial direction.

The rotary bearing which is generally referred to as an azimuth bearingmakes it possible—by means of the tracking drive—to adjust the rotorwhich receives the wind power, in such a way that, depending on therespective wind direction, the highest level of efficiency is achievedand in addition, when the installation is stopped, the loading on allcomponents of the installation is kept as low as possible. Usually, therotary bearing which must be of large diameter in high-output wind powerinstallations comprises a rotary ball-type connection (DE 41 04 137 C2and DE 196 29 168 C1). Because generally only slight movements are to beeffected about the axis of the pylon in the tracking movement of themachine head but considerable loads have to be carried more specificallywhen relatively high wind speeds are involved, that results inconsiderable static or quasi-static pressures in relation to surfacearea, within the rotary ball-type connection. Added to that is the factthat naturally—and usually advantageously—a rotary ball-type connectionopposes only a low level of resistance to the rotary movement, whichhowever in the case of the azimuth bearing has the result that themachine head is involved in a ‘nervous, jerky’ backward and forwardmovement when the wind direction experiences rapid changes, for examplewhen the wind is gusty; the attempt is made to remedy that by means ofdamped control of the tracking movement or also by using mechanicalbrakes (DE 41 04 137 C2, 196 29 168 C1 and 198 14 629 A1).

In comparison therewith, the plain bearing according to the invention issubstantially better suited to carrying high forces when small movementsare involved. In the present case however there is also theconsideration that the sliding friction in the bearing produces a kindof natural damping of excessively hectic tracking movements. Stillfurther: because the static friction which is opposed to the beginningof a tracking movement is always greater than the sliding friction whichoccurs after the static friction has been overcome, substantiallyirrespective of the material pairing involved, the tracking movement isentirely suppressed in the event of short-term and/or minor changes inwind direction.

In the state of the art, plain bearings have already been used asazimuth bearings for wind power installations, but only in relation torelatively small installations (Hau, ‘Windkraftanlagen’, [‘Wind PowerInstallations’], page 270). Their above-discussed control function isneither recognised therein, nor could it discernibly appear.

The plain bearing can carry vertical forces which occur in the axialdirection both in the direction of an applied load and also in thelifting-off direction. The anti-friction linings can be both pinned andalso glued to the annular rib. For inspection of the anti-frictionlinings and therewith the rotary bearing and If necessary forreplacement of the anti-friction linings or the segments of theco-operating bearing components, the arrangement preferably has at leastone closable maintenance opening in the machine head flange (whichopening can be closed for example by a plug); by virtue of rotating themachine head, it is possible to check over and maintain the entirerotary bearing.

The anti-friction linings preferably comprise a metal-plastic compositewith a steel back and a pimpled acetal copolymer bearing surface.

Lubrication of the plain bearing is effected from below upwardly bymeans of continuous lubrication cartridges; old grease is delivered tothe exterior on the top side of the bearing, and collected. For thatpurpose, below the annular groove into which the annular rib engageswith the anti-friction linings, a peripherally extending seal is fittedinto the machine head flange, which seals off the gap with respect tothe pylon head flange. At the top side, a sealing strip is fixed abovethe annular groove to the machine head flange in such a way that itbears with its free region on the top side of the pylon head flange.

The drawing illustrates the invention in embodiments thereof. In thedrawing:

FIG. 1 is a diagrammatic cross-section of a plain bearing according tothe invention in a general form,

FIG. 2 is a plan view on a reduced scale of the segmented outer ringwith the radially inwardly directed annular rib of the plain bearing inFIG. 1,

FIG. 3 is a view in cross-section through the machine head housing of apylon-supported wind power installation with the machine head flange andthe upper end of the pylon with the pylon head flange, in the separatedcondition of the plain bearing,

FIG. 4 is a view substantially corresponding to FIG. 3 on a somewhatenlarged scale, in the assembled condition,

FIG. 5 shows a partial view on an enlarged scale of the bearingcross-section (circular portion indicated at ‘X’ in FIG. 4), and

FIG. 6 is a diagrammatic plan view of a part of the machine head withthe tracking drive.

FIG. 1 diagrammatically shows the configuration and arrangement of aplain bearing according to the invention with an outer race or ring 104which is fixed to a support structure 101 which is not shown in greaterdetail. The outer ring 104 is extended radially inwardly in an annularrib 106 which is of a trapezoidal, radially inwardly taperingcross-section. The substantially upwardly and downwardly facing sidefaces of the annular rib 106 are lined with anti-friction linings in theform of anti-friction lining segments 108 which are fixedly butreleasably mounted to the annular rib, for example by pins or byadhesive. The same applies in regard to anti-friction lining segments107 which are arranged at the inner peripheral surface of the annularrib 106.

The annular rib 106 with its anti-friction lining segments 107, 108engages into an inner race or ring 122 which is part of a structure 110rotatable about the axis 112, and which with the outer ring 104 formsthe plain bearing.

FIG. 2 shows that and how the outer ring 104 is subdivided into segments104′ which are fixed to the support structure 101 by means of screws123. The lateral relative orientation of the segments 104′ canadditionally be ensured by groove-and-tongue connections or the like. Itis possible to see, on the rib portions 106′ of the annular rib 106, theanti-friction lining segments 108 which, in the event of wear or othermaintenance, can be removed together with the outer ring segments 104.That procedure can be made easier by virtue of the fact thatpower-operating lifting means (not shown) are arranged between thesupport structure 101 and the inner bearing ring 122 (FIG. 1), which areto lift the structure 110 only in the stationary condition and in thatway to permit release of the screw connections 123 and to allow theindividual segments 104′ to be removed in a radially outward direction.

FIGS. 3-6 show the use of a plain bearing according to the inventionbetween the pylon and the machine head of a wind power installation.Fixed to the upper end of the supporting pylon 1 is a pylon head flange2 comprising a flange ring 3 and a bearing outer race or ring 4; theparts 3 and 4 are connected together by screws 5. The outside of thebearing outer ring 4 is provided with an outside tooth arrangement 30into which the pinions of gear motors 31 (FIG. 6) engage and in that wayform the tracking drive.

In the usual manner, the machine head housing 10 has a mounting means 11for the rotor (not shown) and in its interior encloses the mechanicaland electrical units (also not shown) of the wind power installation.Fixed to the machine head housing 10 at the underside thereof is amachine head flange 20 which comprises a ring 21 and a bearing innerrace or ring 22. The parts 21 and 22 are connected to each other andalso to the machine head housing 10 by means of screws 23.

Provided in the bearing inner ring 22 on the outside thereof is anannular groove 24 which is partially bordered by the ring 21. In theassembled condition (FIG. 4), engaging into the annular groove 24 is anannular rib 6 which is provided at the inside on the bearing outer ring4 of the pylon head flange 2 and which is provided with part-cylindricalanti-friction lining segments 7 for radial guidance and, at the top andat the underneath, with circular ring anti-friction lining segments 8for vertical guidance. The anti-friction lining segments 7, 8 are gluedto the corresponding surfaces of the annular rib 6 and also fixed bypins (FIG. 5). In the direction parallel to the axis 12 of the pylon,the thickness of the annular rib 6 (including the anti-friction liningsegments 8) is slightly less than the internal width of the annulargroove 24 so that, depending on the respective direction of the verticalforce, either the upper or the lower anti-friction lining segments bearagainst the associated walls of the annular groove 24.

Provided in the machine head flange 20 is a maintenance opening 25which, even in the assembled condition and in operation of the windpower installation, permits inspection and possibly maintenance orreplacement of the anti-friction lining segments 7, 8. In addition,fitted into the bearing inner ring 22 beneath the annular groove 24 is aseal 26 which co-operates with the corresponding surface of the bearingouter ring 4 (see FIG. 5). A lip seal 27 which is let into the ring 21bears against the top side of the bearing outer ring 4 as part of thepylon head flange 2.

As already indicated above, the tracking drive is formed by fourelectric motors 31′ which engage with their pinions into the tootharrangement 30 on the bearing outer ring 4 (FIG. 6).

What is claimed is:
 1. A plain bearing for the transmission of highaxial forces and low flexural moments with slight relative movementsbetween the co-operating bearing components, in which an annular rib (6;106) arranged on one co-operating bearing component (4; 104) engagesinto an annular groove (24; 124) provided on the other co-operatingbearing component (22; 122) and the annular rib (6; 106) is providedwith anti-friction linings (7, 8; 107, 108) on its free side facescharacterised in that the anti-friction linings (7, 8; 107, 108) aresubdivided segment-like and fixedly but releasably connected to the rib(6; 106).
 2. A plain bearing according to claim 1 characterised in thatthe annular rib (6; 106) is of an outwardly convergent trapezoidalcross-section.
 3. A plain bearing according to claim 1 or claim 2characterised in that the anti-friction lining segments (7, 8; 107, 108)comprise a metal plastic composite with a steel back and pimpled acetalcopolymer bearing surface.
 4. A plain bearing according to at least oneof the preceding claims characterised in that one of the co-operatingbearing components (4; 104) is also subdivided segment-like and thesegments (104′) are individually releasable from their compositeassembly.
 5. A plain bearing according to claim 4 characterised in thatthe annular rib (6; 106) which is lined with the anti-friction linings(7, 8; 107, 108) is subdivided into segments (106′) and engages radiallyfrom the outside into the inwardly disposed annular groove (24; 124). 6.A wind power installation comprising a plain bearing according to atleast one of the preceding claims between a pylon-supported machine head(10) and the pylon head (1), wherein provided between the pylon head andthe machine head is a tracking drive (30, 31) for rotation of themachine head about the vertical axis of the pylon in dependence on winddirection, and wherein the plain bearing is adapted to guide the machinehead (10) in the radial direction and the axial direction relative tothe pylon axis (12).
 7. A wind power installation according to claim 6characterised in that in a direction parallel to the axis the totalthickness of the annular rib (6) (including the anti-friction liningsegments 8) is slightly smaller than the internal width of the annulargroove (24).
 8. A wind power installation according to claim 6 or claim7 characterised in that at least one closable maintenance opening (25)is provided in the machine head flange (20) forming the one co-operatingbearing component.
 9. A wind power installation according to one ofclaims 1 to 6 characterised in that there are provided stationarypower-operated means for relieving the load on (lifting) theco-operating bearing components (4, 22; 104, 122) in the stationarycondition when replacing the segments (104′, 106′).